Autism link from older fathers to grandchildren

Updated
March 23, 2013 09:34:00

An international study has found that the grandchildren of older fathers have an increased risk of developing autism. The researchers say a 'silent mutation' may be passed through their children to their grandchildren.

ELIZABETH JACKSON: An international study has found that the grandchildren of older fathers have an increased risk of developing autism.

The researchers say a silent mutation might be passed through their children to their grandchildren.

Professor John McGrath of the Queensland Brain Institute was one of the authors of the study, and he's speaking here to Will Ockenden.

JOHN MCGRATH: Over the last three to five years, there's been strong evidence showing that the offspring of older men have an increased risk of autism.

And what we've done for the first time is to take that across three generations. So it's not only the immediate sons and daughters of men, it's their grandchildren as well, and that suggests strongly that there are mutations or some type of effect that's skipping a generation.

WILL OCKENDEN: So how is it skipping generations?

JOHN MCGRATH: As a man ages there are more chances for mutations or mistakes, genetic mistakes, to accumulate.

So some of these mutations may be silent and hidden, and some of them may contribute to alter brain development. And what this new study suggests is that some of these mutations may not penetrate, they may not cause autism, but they still contribute to a mutational load, a burden. And eventually, they can be a straw that breaks the camel's back, and the offspring have too many mutations to - they have sub-optimal brain development, and that's what we found.

WILL OCKENDEN: So does that mean autism could run in families?

JOHN MCGRATH: It does. Autism, like nearly all types of neuro-developmental disorders and mental disorders, does have a genetic or familial aspect but as well as that, we know that there are environmental factors.

These studies looking at the age of the father are almost certainly being linked to mutations in the germ cell, or the sperm, that the fathers are handing down.

And I think the key issue for our community and for the listeners is that we know that the biological clock ticks for women and now we know that the biological clock ticks for men as well. And the offspring of older men and, our new paper has shown, that the grandchildren of older men bear a slightly increased risk of having autism.

WILL OCKENDEN: It seems that there are more cases of autism in recent years than in years gone by. Could this provide some of the reasons for that?

JOHN MCGRATH: It could, but probably - most researchers feel that the increased incidence and prevalence of autism is due to better detection.

So parents and the general community and general practitioners are more aware of it. And the other aspect, really important aspect, is that the boundaries of where we draw the line to say this person has or has not autism have changed.

So sometimes when you see curves that suggest that the incidence of autism is going up, it may just be a simple reflection that we're getting better at spotting it.

ELIZABETH JACKSON: And that's Professor John McGrath of the Queensland Brain Institute speaking there to Saturday AM's Will Ockenden.